In general, a video surveillance system called as a CCTV (Closed Circuit Television) uses at least one camera. Such a video surveillance system has been employed in a variety of fields for surveillance and security. Recently, the existing analog surveillance cameras are being replaced by high performance digital network cameras of a high performance to which a video compression technology is applied. Moreover, an intelligent camera further including video recognition and event detection functions are on the rise as a next-generation camera. As such, the technical development of surveillance cameras becomes a major issue in the related fields.
Such functional sophistication of the video surveillance system causes side effects to become social problems. Among the social problems, it is a typical problem that personal (or private) information is revealed. Actually, videos of a CCTV within a special district are being originally provided to users by several portal sites without filtering characters in the videos. As a result, it is disclosed the private information regarding whereabouts of an individual in a specific time band. Due to this, the privacy of individuals may be violated.
In order to prevent the problem described above, it is necessary for the video surveillance system to employ an encryption function which encrypts real-time surveillance video to transmit same and allows only an authorized person to watch the encrypted real-time surveillance videos using a decryption key. Such an encryption function may be applied to the video surveillance system in two methods.
First, the whole of an video can be encrypted. This full video encryption scheme enables the video itself to be not recognized visually without decryption. Alternatively, regions-of-interest (ROI) encryption scheme called as privacy masking can be used. The ROI encryption scheme extracts and encrypts regions, which are capable of violating individual privacy such as the face of a person, from a video using a video recognition algorithm possible to recognize the face of a person.
In the former, the entirely encrypted video may cause some problems. Actually, a control center generally divides video monitoring personnel into authorized personnel capable of watching normal videos and unauthorized personnel who performs monitoring limited videos. In this case, it is unnecessary for the unauthorized personnel to perform monitoring the limited videos because the limited videos itself is not identified. Further, in case existent information such as geographic information or traffic information needs to be provided to general users through videos, the entirely encrypted videos can prevent the exposure of personal information but cause information not to be provided. Moreover, if full video encryption is continuously performed in the system for a long time, resources of the system may be wasted to encrypt even unimportant information.
Because of such a property of the video information, only a desired region within a video is generally encrypted by the latter one of the above-mentioned two encryption schemes to be transmitted. Further, an authorized person of the receiving side can generally decrypt and identify the partially encrypted video when a specific event occurs and it is necessary to distinguish a private person related to the specific event. In other words, only desired information is encrypted depending on the content of a video.
However, a serious problem may be overlooked in the current methods even though the video is encrypted depending on the content of the video. Specifically, a part of the video which includes a factor capable of invading individual privacy can be screened for a person exposed to the video, but other persons watching such a partially screened video cannot be considered.
For example, a video including a violent or abhorrent event such as a violent incident, a special theft, a sexual offense, a throwing/burning oneself to death, a human/vehicle accident or other can force a person watching the video to receive regardless of her/his intent and furthermore undergo a considerable psychological impact. Actually, in recent, a violent incident video is broadcasted without filtration through a news channel and arouses a strong storm of public criticism.
Of course, broadcast content providers or web-based VoD (Video-on-Demand) services may previously shield the above-mentioned harmful video information. However, the video surveillance system transmitting and receiving videos in real time can always cause a leakage of such harmful video information. If an encryption scheme for protecting only personal information is applied to the video surveillance system, the privacy of a person taking any action can be protected by the encrypted video, but the action itself must be exposed to other persons. Moreover, if the above-mentioned action is harmful to other persons, it is necessary to prevent a video with such an action from being identified by other persons.